SIMULATION STUDIES OF GE SURFACE SEGREGATION DURING GAS-SOURCE MBE GROWTH OF SI SI1-XGEX HETEROSTRUCTURES/

Simulation studies of Ge surface segregation have been made and compar ed to experimental results during gas source MBE (GSMBE) of Si/Si1-xGe x heterostructures. Segregation kinetics were examined through simulat ions using a two-site exchange model. The influence of surface hydroge n during GSMBE was investigated in terms of the energy parameters in t he model; specifically, the kinetic barrier height, E1, and the Gibbs heat of segregation, DELTAG(seg). Results indicate that the addition o f surface hydrogen to the system suppresses segregation due to a lower ing of the apparent Gibbs heat of segregation, rather than increasing the kinetic barrier. Simulations were also performed to study the rela tive bulk and surface Ge concentrations, an important consideration wh en comparing in situ RHEED intensity oscillation data, which measures solely surface phenomena, with ex situ techniques such as SIMS which m easure the final static concentration profile following growth.